The vehicle control system according to the invention is provided for transportation machines and construction machines, in particular earth moving machines or traffic route construction machines. Such machines are used, for example, for road construction, particularly for fabricating water gullys, boundary walls, curb stones or road coverings. Material-removing and material-shaping machines such as caterpillar bulldozers, excavators, rotary cultivators and rollers, or transport machines such as feeding apparatuses and truck mixers are also intended to be equipped with the vehicle control system according to the invention.
In vehicle control systems having the specified applications, in particular precision in the positioning of the machine is required. The vehicle is guided according to a predefined route in dependence on determined actual position data.
In order to guide the machine along a predefined route and, if appropriate, also position its tools vertically, it is customary, inter alia, to extend a reference line, for example a wire cable, along which guidance takes place. This is carried out with distance sensors which are linked to the control system of the machine.
Since the scanning of the reference lines requires that the area to be worked is measured and staked out before the start of the installation works, and is therefore very costly, the machine can alternatively be controlled by means of a position determining system. For example, the position of the machine is determined by means of one or more GPS receivers which are arranged on it. However, the position data which is received by the navigation satellites contains an error or inaccuracy which is unacceptable depending on the use. The accuracy is usually greatly improved by virtue of the fact that what is referred to as a differential global positioning system (DGPS) is used. This makes use of the fact that the errors which occur at a specific point in time in the relatively close surroundings virtually correspond during the determination of the position. The GPS receivers in the machine therefore receive correction data which is acquired by means of a reference station at another location which is not too far away. The reference station is here a further GPS receiver, and the location is one whose position is exactly known. The position data received from the reference station is compared with the exactly known position, and a difference is determined between said positions and is communicated to the imprecise GPS receivers. This technology is described in terms of the generic type, for example, in U.S. Pat. No. 8,400,351 and DE 10 2009 058 106 A1, and requires not only complex and expensive equipment but also special knowledge on the part of specialist personnel.
An alternative form of positioning machines which is independent of satellites is also known, in which alternative, as described in EP 2 006 448 A1, the actual position of a reflector which is mounted on the vehicle and whose position is continuously measured by means of a tachymeter is compared with a reference position, for example from a model of the terrain, wherein control instructions are derived from the comparison. The disadvantage with this method is the continuous dependence of the control on the stationary tachymeter and a tracking mechanism (tracking) which is potentially susceptible to interference.
The specified position- or location-determining methods for performing control are developed for high levels of accuracy and require corresponding complex components and data processing methods. For this reason, only the machines which operate with an extremely high level of accuracy are controlled in this way.